Cordierite Sintered Body Composition for Mirror-Flat Substrates
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Solution Overview
Problem
Cordierite sintered bodies with added sintering auxiliary agents have surface irregularities due to different phases, making surface flatness difficult to achieve, while those without auxiliary agents have closed pores that also hinder surface flatness, and existing surface acoustic wave devices lack detailed information on substrate surface conditions.
Innovation Solution
A cordierite sintered body is manufactured using a hot press method with a specific composition of MgO, Al2O3, and SiO2, achieving a high surface flatness by minimizing other phases and porosity, and a composite substrate is formed with a high joining area rate for improved thermal expansion properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If sintering auxiliary agents are added to cordierite sintered body, then sintering properties and grain growth are improved, but surface flatness deteriorates due to surface irregularities from different phases
Solution Approach 1:
The invention removes sintering auxiliary agents from the cordierite sintered body composition. By using only pure cordierite raw materials without any sintering aids, the patent eliminates the formation of secondary phases that cause surface irregularities, thereby achieving high surface flatness while maintaining manufacturability through optimized sintering conditions
Solution Approach 2:
The invention changes the compositional parameters by setting the cordierite content to 100% and eliminating all sintering auxiliary agents. This parameter change ensures that no secondary phases form during sintering, preventing surface irregularities and achieving high surface flatness
2Manufacturing precision
If sintering auxiliary agents are not added to cordierite sintered body, then surface irregularities from different phases are reduced, but closed pores form that hinder surface flatness
Solution Approach 1:
The invention optimizes the sintering temperature parameter to 1700°C or higher, which provides sufficient thermal energy for complete densification and elimination of closed pores without requiring sintering auxiliary agents. This temperature parameter change enables achieving both high surface flatness and low porosity simultaneously
Solution Approach 2:
The invention uses a composite raw material system consisting of cordierite powder combined with specific amounts of alumina and silica powders. This composite approach facilitates complete reaction and densification at high sintering temperatures, eliminating pores while maintaining a single-phase cordierite structure for high surface flatness
3Device complexity
If main substrate and auxiliary substrate are directly joined in surface acoustic wave device, then device structure is simplified, but joining quality is insufficient due to lack of surface condition control
Solution Approach 1:
The invention specifies precise surface roughness parameters (Ra of 0.1 μm or less) for both main and auxiliary substrates before joining. By controlling this surface parameter, the patent ensures high-quality direct joining without requiring additional intermediate layers, maintaining structural simplicity while achieving reliable joint strength
Solution Approach 2:
The invention creates a standardized surface condition specification that can be replicated for both main and auxiliary substrates. By establishing uniform surface roughness requirements for both components, the patent enables consistent and reliable joining quality across different device productions
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The cordierite sintered body achieves high surface flatness and improved thermal expansion characteristics, enhancing the performance of surface acoustic wave devices and other electronic components by reducing frequency temperature dependence and increasing stability.
Implementation Method 1
a molded body is sintered in a hot press method in an inert gas atmosphere
Implementation Method 2
a molded body is sintered in a hot press method in an inert gas atmosphere so that a cordierite sintered body is obtained
Data Source
AI summary
In an X-ray diffraction diagram of a cordierite sintered body of the present invention, the ratio of the total of the maximum peak intensities of components other than cordierite components to the peak top intensity of the (110) plane of cordierite is 0.0025 or less. Since having a significantly small amount of different phases other than the cordierite components, this cordierite sintered body has a high surface flatness when the surface thereof is mirror-polished.